nuttx/net/tcp/tcp_close.c

/****************************************************************************
 * net/tcp/tcp_close.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>
#ifdef CONFIG_NET_TCP

#include <errno.h>
#include <debug.h>
#include <assert.h>

#include <nuttx/semaphore.h>
#include <nuttx/net/net.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/tcp.h>

#include "netdev/netdev.h"
#include "devif/devif.h"
#include "tcp/tcp.h"
#include "socket/socket.h"

/****************************************************************************
 * Private Types
 ****************************************************************************/

struct tcp_close_s
{
  FAR struct devif_callback_s *cl_cb;     /* Reference to TCP callback instance */
  FAR struct socket           *cl_psock;  /* Reference to the TCP socket */
  sem_t                        cl_sem;    /* Signals disconnect completion */
  int                          cl_result; /* The result of the close */
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: tcp_close_eventhandler
 ****************************************************************************/

static uint16_t tcp_close_eventhandler(FAR struct net_driver_s *dev,
                                       FAR void *pvconn, FAR void *pvpriv,
                                       uint16_t flags)
{
  FAR struct tcp_close_s *pstate = (FAR struct tcp_close_s *)pvpriv;
  FAR struct tcp_conn_s *conn = (FAR struct tcp_conn_s *)pvconn;

  DEBUGASSERT(pstate != NULL);

  ninfo("flags: %04x\n", flags);

  /* TCP_DISCONN_EVENTS:
   *   TCP_CLOSE:    The remote host has closed the connection
   *   TCP_ABORT:    The remote host has aborted the connection
   *   TCP_TIMEDOUT: The remote did not respond, the connection timed out
   *   NETDEV_DOWN:  The network device went down
   */

  if ((flags & TCP_DISCONN_EVENTS) != 0)
    {
      /* The disconnection is complete.  Wake up the waiting thread with an
       * appropriate result.  Success is returned in these cases:
       *
       * * TCP_CLOSE indicates normal successful closure.  The TCP_CLOSE
       *   event is sent when the remote ACKs the outgoing FIN in the
       *   FIN_WAIT_1 state.  That is the appropriate time for the
       *   application to close the socket.
       *
       *   NOTE:  The underlying connection, however, will persist, waiting
       *   for the FIN to be returned by the remote in the TIME_WAIT state.
       *
       * * TCP_ABORT is less likely but still means that the socket was
       *   closed, albeit abnormally due to a RST from the remote.
       *
       * * TCP_TIMEDOUT would be reported in this context if there is no
       *   ACK response to the FIN in the FIN_WAIT_2 state.  The socket will
       *   again be closed abnormally.
       *
       * This is the only true error case.
       *
       * * NETDEV_DOWN would indicate that the network went down before the
       *   close completed.  A non-standard ENODEV error will be returned
       *   in this case.  The socket will be left in a limbo state if the
       *   network is taken down but should recover later when the
       *   NETWORK_DOWN event is processed further.
       */

      if ((flags & NETDEV_DOWN) != 0)
        {
          pstate->cl_result = -ENODEV;
        }
      else
        {
          pstate->cl_result = OK;
        }

      goto end_wait;
    }

#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
  /* Check if all outstanding bytes have been ACKed */

  else if (conn->tx_unacked != 0 || !sq_empty(&conn->write_q))
    {
      /* No... we are still waiting for ACKs.  Drop any received data, but
       * do not yet report TCP_CLOSE in the response.
       */

      dev->d_len = 0;
      flags &= ~TCP_NEWDATA;
    }

#endif /* CONFIG_NET_TCP_WRITE_BUFFERS */

  else
    {
      /* Drop data received in this state and make sure that TCP_CLOSE
       * is set in the response
       */

      dev->d_len = 0;
      flags = (flags & ~TCP_NEWDATA) | TCP_CLOSE;
    }

  UNUSED(conn);           /* May not be used */
  return flags;

end_wait:
  pstate->cl_cb->flags = 0;
  pstate->cl_cb->priv  = NULL;
  pstate->cl_cb->event = NULL;
  nxsem_post(&pstate->cl_sem);

  ninfo("Resuming\n");
  return flags;
}

/****************************************************************************
 * Name: tcp_close_txnotify
 *
 * Description:
 *   Notify the appropriate device driver that we have data ready to
 *   be sent (TCP)
 *
 * Input Parameters:
 *   psock - Socket state structure
 *   conn  - The TCP connection structure
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

static inline void tcp_close_txnotify(FAR struct socket *psock,
                                      FAR struct tcp_conn_s *conn)
{
#ifdef CONFIG_NET_IPv4
#ifdef CONFIG_NET_IPv6
  /* If both IPv4 and IPv6 support are enabled, then we will need to select
   * the device driver using the appropriate IP domain.
   */

  if (psock->s_domain == PF_INET)
#endif
    {
      /* Notify the device driver that send data is available */

      netdev_ipv4_txnotify(conn->u.ipv4.laddr, conn->u.ipv4.raddr);
    }
#endif /* CONFIG_NET_IPv4 */

#ifdef CONFIG_NET_IPv6
#ifdef CONFIG_NET_IPv4
  else /* if (psock->s_domain == PF_INET6) */
#endif /* CONFIG_NET_IPv4 */
    {
      /* Notify the device driver that send data is available */

      DEBUGASSERT(psock->s_domain == PF_INET6);
      netdev_ipv6_txnotify(conn->u.ipv6.laddr, conn->u.ipv6.raddr);
    }
#endif /* CONFIG_NET_IPv6 */
}

/****************************************************************************
 * Name: tcp_close_disconnect
 *
 * Description:
 *   Break any current TCP connection
 *
 * Input Parameters:
 *   conn - TCP connection structure
 *
 * Returned Value:
 *   None
 *
 * Assumptions:
 *   Called from normal user-level logic
 *
 ****************************************************************************/

static inline int tcp_close_disconnect(FAR struct socket *psock)
{
  struct tcp_close_s state;
  FAR struct tcp_conn_s *conn;
  int ret = OK;

  /* Interrupts are disabled here to avoid race conditions */

  net_lock();

  conn = (FAR struct tcp_conn_s *)psock->s_conn;
  DEBUGASSERT(conn != NULL);

#ifdef CONFIG_NET_SOLINGER
  /* SO_LINGER
   *   Lingers on a close() if data is present. This option controls the
   *   action taken when unsent messages queue on a socket and close() is
   *   performed. If SO_LINGER is set, the system shall block the calling
   *   thread during close() until it can transmit the data or until the
   *   time expires. If SO_LINGER is not specified, and close() is issued,
   *   the system handles the call in a way that allows the calling thread
   *   to continue as quickly as possible. This option takes a linger
   *   structure, as defined in the <sys/socket.h> header, to specify the
   *   state of the option and linger interval.
   */

  if (_SO_GETOPT(psock->s_options, SO_LINGER))
    {
      /* Wait until for the buffered TX data to be sent. */

      ret = tcp_txdrain(psock, _SO_TIMEOUT(psock->s_linger));
      if (ret < 0)
        {
          /* tcp_txdrain may fail, but that won't stop us from closing
           * the socket.
           */

          nerr("ERROR: tcp_txdrain() failed: %d\n", ret);
        }
    }
#endif

#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
  /* If we have a semi-permanent write buffer callback in place, then
   * is needs to be be nullified.
   *
   * Commit f1ef2c6cdeb032eaa1833cc534a63b50c5058270:
   * "When a socket is closed, it should make sure that any pending write
   *  data is sent before the FIN is sent.  It already would wait for all
   *  sent data to be acked, however it would discard any pending write
   *  data that had not been sent at least once.
   *
   * "This change adds a check for pending write data in addition to unacked
   *  data.  However, to be able to actually send any new data, the send
   *  callback must be left.  The callback should be freed later when the
   *  socket is actually destroyed."
   *
   * REVISIT:  Where and how exactly is s_sndcb ever freed?  Is there a
   * memory leak here?
   */

  psock->s_sndcb = NULL;
#endif

  /* Check for the case where the host beat us and disconnected first */

  if (conn->tcpstateflags == TCP_ESTABLISHED &&
      (state.cl_cb = tcp_callback_alloc(conn)) != NULL)
    {
      /* Set up to receive TCP data event callbacks */

      state.cl_cb->flags = (TCP_NEWDATA | TCP_POLL | TCP_DISCONN_EVENTS);
      state.cl_cb->event = tcp_close_eventhandler;

      /* A non-NULL value of the priv field means that lingering is
       * enabled.
       */

      state.cl_cb->priv  = (FAR void *)&state;

      /* Set up for the lingering wait */

      state.cl_psock     = psock;
      state.cl_result    = -EBUSY;

      /* This semaphore is used for signaling and, hence, should not have
       * priority inheritance enabled.
       */

      nxsem_init(&state.cl_sem, 0, 0);
      nxsem_set_protocol(&state.cl_sem, SEM_PRIO_NONE);

      /* Notify the device driver of the availability of TX data */

      tcp_close_txnotify(psock, conn);

      /* Wait for the disconnect event */

      net_lockedwait(&state.cl_sem);

      /* We are now disconnected */

      nxsem_destroy(&state.cl_sem);
      tcp_callback_free(conn, state.cl_cb);

      /* Free the connection
       * No more references on the connection
       */

      conn->crefs = 0;

      /* Get the result of the close */

      ret = state.cl_result;
    }

  /* Free network resources */

  tcp_free(conn);

  net_unlock();
  return ret;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: tcp_close
 *
 * Description:
 *   Break any current TCP connection
 *
 * Input Parameters:
 *   psock - An instance of the internal socket structure.
 *
 * Assumptions:
 *   Called from normal user-level logic
 *
 ****************************************************************************/

int tcp_close(FAR struct socket *psock)
{
  FAR struct tcp_conn_s *conn = psock->s_conn;
  int ret;

  /* Perform the disconnection now */

  tcp_unlisten(conn); /* No longer accepting connections */
  conn->crefs = 0;    /* Discard our reference to the connection */

  /* Break any current connections and close the socket */

  ret = tcp_close_disconnect(psock);
  if (ret < 0)
    {
      /* This would normally occur only if there is a timeout
       * from a lingering close.
       */

      nerr("ERROR: tcp_close_disconnect failed: %d\n", ret);
      return ret;
    }

  /* Stop the network monitor for all sockets */

  tcp_stop_monitor(conn, TCP_CLOSE);
  return OK;
}

#endif /* CONFIG_NET_TCP */